Extended linear power amplifier systems have been proposed for use in cellular base stations. These systems include a number of linear power amplifier modules producing a corresponding number of output signals that need to be combined into a single high power signal before transmission. Such systems are typically used in communication systems such as in a base site of a radiotelephone system. In such systems, it is desirable that the number of linear power amplifier modules may be any number from a minimum number up to a maximum number of allowable amplifiers. In this manner, the amount of power output by the transmission unit of the base station may be adjusted. In addition, it is desirable that the system provides adequate power amplification efficiency across the entire range of selected amplifiers, i.e. from the minimum number to the maximum number of amplifiers.
Another reason for providing multiple amplifiers is to provide continued operation if one of the amplifiers fails. A conventional method of continuing operation is a method known as load shedding. In the load shedding method, after a fault is detected, all new calls that would be handled by the affected sector associated with the faulty amplifier are blocked and a predetermined percentage of the existing channels are taken out of service. After the fault has cleared, traffic is then returned to normal capacity. Although the load shedding procedure allows for continued operation after a failure condition, it would be desirable if the system could maintain the traffic level prior to the failure and reduce the impact resulting from the failure to call processing.
Accordingly, there is a need for an improved power delivery system and a method of controlling the power delivery system for use in a RF system, such as a cellular system.